Distillation of metals



Oct. 11, 1955 T. R. A. DAVEY 2,720,456

DISTILLATION OF METALS Filed June 4, 1953 5 Sheets-Sheet l fin 1. 2a

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Oct. 11, 1955 'r. R. A. DAVEY 2,720,456

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United States Patent 2,720,45 DISTILILATION or METALS ThomasRonald AlbertDavey, Poi-t Pi'rie; South Australia, Australia, assig'uor to" The Broken Hill Associated Sm'elters Proprietary Limited; Melbourne, Victoria",

is not limited to theseparation and recovery of zinc from r zinciferous lead, especially lead which has previously been desilverised by incorporating zinc therein.

This application is acontinuation-in-part of application Serial No; 174,484, filed Jul-y 18, 1950, now abandoned.

The general object ofthis invention is to provide irnprovements in the separation of a' relatively volatile constituerit from a m'oltenmetal complex under a low pressure and particularly in'the recovery ofizinc from zinciferous lead. t j j One particular object is to provide an improved method whereby the evaporated constituent is condensed in the liquid conditions andis progressively discharged from the vacuum chamber.

Another particular object is to provide a distillation method and apparatus wherein" the evaporated constituent is condensedin the liquid condition on acondenser formed of the same metal as saidevaporatedconstituent, thereby obviating: the necessity for close andaccurate control of the temperature of-thecoride'nser.

A further object is to provide a method and:apparatus wherein the condenser is formed Sltll'z Another object is to provide improved means whereby the molten metal passes throughanevaporating zone in an attenuated condition, theexpressionattenuatedcondition being intended to comprehenda'riycondition in which the exposed or freesurface areasis'large in proportion to the volume of the metal. Q i

Other objects are to: provide improved methodsand arrangements for-removing the condensed liquid metal The invention as applied to the separation ofzinc metal from desilverised= lead bullion is hereafter described with reference to the accompanying? drawings in whichf Figure l is a' view in sectional elevation ofionepreferred form of distillation a'p'paratus incorporating the invention, 1 Figure 2 is aviewhalf in plan and half in sectional plan onthe liiie' ofiFigured Figure 3 is a sectional view to a larg'er sca'l e of the Figure- 4 is a sectional view-t6 a larger scale of a vapor trap and appurtenant partsshown' in Figure 1 Figures 5, 6 and 7 are views in sectional elevatioti 'siniilar to Figure l and showrnodifiedform'softhe distillation apparatus and zincrembVal mEansQaiiil Figure 8' is a view in sectional elevationshowing a still distributing the molten metal further arrangement for removing: the zinctfrom the'va'cr wardly through' the topto adjacent the bottom thereof.

The upper end portion of the chamber projects through the top of a brick structure 21 which encloses the remaining portion of the chamber and the latter is supported on top of this structure by a plurality of supporting and levelling screws 22 which are fitted to external lugs 10 on the wall of the chamber.

The said vacuum pipe forms the inner Wall of an annular downwardly convergent water-cooled condenser core 12, through which cooling water may be circulated asindicated in Figure 1.

A distributing tube 13 of downwardly convergent frusto-conical form and relatively large diameter is arranged concentrically within the chamber about the condenser core 12 and has its lower end welded to the bottom of the chamber. Thus a relatively narrow annular well is formed within the chamber around the distributing tube:

The upper end of the distributing tube 13 is disposed adjacent to but is spaced from the top of the chamber and said upper end ismachined so as to form a plane surface thereon:

This distributing tube is surmounted by a coaxially disposed control ring 14 of equivalent diameter and same are spaced apart so as to form therebetween a narrow annular slot 15 through which the molten metal may pass from the annular well to the inner surface of the tube. For this purpose the control ring may be supported on the upper end of the distributing tube by a plurality of spacing members such as wires 16 which are arranged at suitable intervals therebetween.

The distributing tube 13 is provided near its lower end with a flexible joint 17 formed of sheet metal and such tube is supported near its upper end by a plurality of external' lugs 18 thereon which rest upon brackets 19 projecting from the inner Wall of the chamber 10. Such lugs and brackets are retained together by pins 20 which extend through clearance holes therein.

As the internal supporting brackets 19 are disposed adjacent tothe external lugs 10 for the supporting and levelling screws 22, it will be evident that by adjusting-the latter, the upper end of the distributing tube 13 may be arranged horizontally.

The moltenmetal to be treated is supplied to the aforesaid annular well by a pipe 23 which has its inlet end submerged in a bath 24 of molten lead bullion having its free: surface exposed to atmospheric pressure and located at such a position that the upper surface of a barometric column supported thereby is disposed below the level of the top of the control ring 14and somewhat above the l'evel ef thenarrow annular slot 15.

Thus when the apparatus is in use molten metal continuously passes into the annular well within the chamher 1 0 and the free surface thereof is disposed above the level of theslot 15 as shown in Figures 1 and 3. The molten metal thus continually passes through the annular slot and then flows" downwardly over the convergent inner surface of the distributing tube 13 in the form of a thin tubular stream.

Preferably and as shown in Figure 1 of the drawings, thedischarge end of the supply pipe 23c'ommunicates with an open ended vertical passage 36 arranged within the annular well so as toobviate' undue disturbance of the metal in the well by the incoming metal.

A-n" annular retaining wall 25 which projects upwardly fromthe bottom of the chamber 10 forms the inner perip'hery of a receiving channel 25 for the molten metal discharged from the lower end of the distributing tube 13 and a bullion discharge pipe 26 communicates at its upper endtherewith, while its lower end projects into a bath-'27 of treated metal, the length of the discharge pipe above thesurface ofthe bath 27 being greater than the I height of a" barometric column of lead.

A zinc discharge pipe 28 depends vertically from the centre of the bottom of the chamber and its upper end projects into a well 10 and is enclosed within a bell member 29 so as to form within the well 10 a trap of molten zinc which separates the interior of the chamber from the interior of the zinc discharge pipe 28. The lower end of this discharge pipe 28 is submerged in a bath 30 of molten zinc and the length of such pipe is greater than that of a barometric column of zinc as indicated in the drawings.

Flues 26' and 28', through which furnace gases may be passed surround the discharge pipes 26 and 28 and such flues discharge into the annular space around the vessel 10, while in addition the structure 21 is provided with inlet and outlet flues 21' and 21 respectively for furnace gases whereby the chamber may be maintained at the requisite temperature. As the external heat so applied is conducted through the molten metal to the distributing tube 13, substantial inequalities of temperature in, and excessive distortion of, the latter are avoided.

The aforesaid trap of molten zinc in the well 10 thus enables the zinc in the discharge pipe 28 and bath 30 to be maintained at a temperature sufficiently above the melting point to facilitate the casting of the metal without subjecting the interior of the chamber 10 to the vapor pressure thereof.

A circular metal baffle plate 31 is arranged horizontally within the chamber above the well 10 and below the lower end of the condenser and vacuum pipe to serve the functions hereafter explained.

In operation therefore desilverised bullion preferably at a temperature about 500 C.-700 C. passes continuously into the annular well of the chamber 10 through the supply pipe 23 and thence from the latter through the narrow annular slot at the top of the distributing tube 13, so that the molten metal then flows downwardly over'the inner surface thereof in the form of a thin tubular stream disposed concentrically about the condenser I 'in an evaporating'zone defined by the said inner surin the annular receiving channel 25 at the bottom of the chamber and is discharged through the pipe 26.

The zinc vapor so evolved is initially condensed on and around the periphery of the condenser core 12 in the form of a collar of solid metal designated 35 in Figure 1 and it will be evident that as this collar increases in thickness the temperature at its surface progressively rises due both to its closer proximity to the surrounding evaporating surface and to the latent heat given up by the condensing zinc. This process continues until the surface ofthe collar of condensed zinc is maintained at the melting point of zinc and thereafter the zinc vapor is condensed thereon in liquid form and flows downwardly thereover until it drops from the lower end of the collar.

The water-cooled zinc collar 35 thus formed in situ during the initial stage of a run accordingly constitutes the condenser on which the zinc vapor is subsequently condensed in the liquid condition and as such it forms a part of the apparatus in which the normal operation is performed. Moreover, it will be evident that if desired the solid zinc condenser may be preformed similarly to the other parts of the apparatus, though it is convenient to form it in situ as described.

It is important that the molten surface of the zinc collar should not extend so close to the evaporating surface as to recontaminate the downwardly flowing bul-- lion and thus the invention involves correctly proportioning the diameters of the distributing tube and condenser core to suit the required operating condition but such proportions may be readily determined with sufficient accuracy by one skilled in the art.

The liquid zinc which drops from the lower end of the condenser as above described falls onto the baffie plate 31 and passes around the edges thereof to the well 10 arranged therebelow.

This plate is maintained approximately at the temperature of the melting point of zinc (viz. 420 C.) by the liquid zinc which drops thereonto while the temperature of the zinc in the well may be somewhat higher due to the necessity for avoiding solidification of the metal therein. Under such conditions 'zinc would tend to evaporate from the metal in the well 10 but in rising the vapor contacts the undersurface of the cooler baffle plate 31 and is thus recondensed thereon. 7

Any uncondensed Zinc vapor is withdrawn through the vacuum off-take pipe 11 and as the wall thereof is cooled by the water circulating through the condenser, of which it'forms the inner wall, such vapor is condensed thereon in the solid form. Thus the vacuum pipe serves also as a-zinc trap which prevents deposition of the metal in the vacuum pump. It will also be apparent that the axial disposition of the vacuum pipe tends to maintain uniform conditions within the chamber.

The solid metal which thus accumulates on the wall of the vacuum pipe is removed at intervals either by heating such wall or by mechanical action. In either case the dislodged metal falls downwards onto the bafile plate 31 and is remelted thereon whereby it passes therefrom to the well '10 For this purpose electric heating elements (not shown) may be arranged around the vacuum pipe so that same may be energised at suitable intervals.

Alternatively, an axially .reciprocable scraper device such as that indicated at 40 in Figure 1 may be arranged within the vacuum pipe 11 whereby same may be operated at intervals, for example by the supporting rod 41.

The distributing tube 13 is downwardly convergent in-order toensure that the molten metal which overflows the upper end thereof remains in contact with the inner surface of the tube as it gravitates to the bottom of the chamber thus promoting a substantially uniform distribution of the metal by substantially obviating the formation of individual streams or rivulets such as would tend to occur if the surface of the distributing tube were disposed vertically.

Also when the descending stream of molten metal is maintained in contact with the distributing tube due to theconvergent form thereof, the loss of heat due to evaporation of the zinc from the stream is largely compensated by the conduction of heat thereto through the distributing tube from the bullion in the surrounding well. In this way the temperature drop in the molten metal as it passes through the evaporating zone is reduced to about 10 C. to 50 C. depending upon the operating conditions and particularly upon the rate of flow of the metal.

If heat 'were not supplied in this way to the molten metal in the evaporating zone, the temperature drop would be of the order of 150 due both to evaporation of the zinc and radiation to the condenser so that it would then be necessary to supply the bullion to the chamber, at a temperature of about 750 C. in order that it would leave the evaporating zone at a temperature of about 600 C.

While for the foregoing reasons the distributing tube is of downwardly convergent form, the degree of convergence may be quite small. Thus the angle which the sloping wall of the distributing tube makes with the horizontal plane could probably be as high as 89 and as low as 60 or less, the preferred angle being about Similarly the outer surface of the condenser core 12 A is of downwardly convergent form so that the crust 35 of solid zinc which is condensed 'tliereon will alsoi be downwardly convergent and in such circumstances the outer surface thereof tendstobe roughly parallel to the evaporating surface which is the desirable condition to enable zinc vapor to pass without obstruction from each portion of the evaporating. zone to a corresponding portion of the condenser surface. In general it is preferred that the angle between the outer surface of the condenser core and the horizontal plane should be between 50 to 85, the actual angle chosen in any particular case depending principally upon the proportions of the vacuum chamber which may be tall and narrow orshort and wide.

Preferably, the conditions of carrying out the method of the present invention are so controlled that the thickness of the zinc collar 35 is at least one-tenth of the diameter of the distributing, surface. Thus, in a particular installation used for treating 56 tons per hour of desilverised lead bullion at a temperature of approximately 650 C. and containing 0.56% zinc, the distributing tube 13 was 30 inches in internal diameter at the top, 24 inches in diameter at the bottom and 30 inches high, While the water-cooled core of the condenser 12 was approximately 6 inches in maximum diameter and the zinc collar 35 had a diameter of 12 inches or more near the top, i. e. the zinc collar had athickness of ,3 inches or more. Under these conditions, with an indicated vacuum of 100 micronsof mercury, the dezinccd bullion leaving the distributing surface at 600 C. contained about 0.05% zinc, i. era recovery of about 90% of input zinc was obtained. The composition of the distillate recovered averaged 95% zinc and 5% lead, the percentage of lead varying from about 1% to about 10%. As, however, the distillate was returned for use in desilverising softened lead, its variable lead content was unimportant.

It may also be remarked that the desilverised lead being treated contained 0.03% antimony but this was not affected by the treatment.

In order to obtain a useful recovery of zinc in the liquid form, the temperature of the condensing surface must be above but not much in excess of the melting point oftzinc, i. e. 420 10., because the vapor pressure of pure zinc at this temperature is 155; microns and it increases rapidly with the temperature so that at 430 C., for example, the vapor pressure is 2-10 microns; Accordingly, when the pressure -maint'ained Within the chamber is less than 100 microns re-evaporation'of liquid zinc will take place rapidlyif the temperature thereof is materially above 420 C. Also the partial pressure of zinc in lead bullion containing 0.05 zinc at a ter'nperature of 600 C. is 185 microns so that distillation of zinc will not proceed from the bullion to the condenser unless the temperature of the latter is prevented from rising materially above 420 C. v i t The method and apparatus hereinbefore described therefore provide, automatically and simply, the accurate temperature control whichis necessitated-bythe foregoing considerations and thus constitutes a; considerable? advancein the art.

Inthe modified construction shown in Figure 5, the

vacuum pipe 11 is arranged centrally below the chamber 10 and communicates with the bottom thereof.

The pipe-11 is bentlaterally some distancebelow the chamber 10 and then upwardly from the outer end of such lateral portion in the form of a U tube. The lower end portion of this U bend in the vacuum pipe is-maintained approximately at the temperature of the melting point of Zinc (420; C.) by a surrounding bath 45which is maintained at the required temperature. Whenthe apparatus is used in a lead refinery, this bath may conveniently be composed of molten leadv but any other suitable material may be used for the purpose.

A well 46 formed in the bottom of the U bend and centrally i below the condenser 12- is connected by an'upwardly inclinedtube t'l to theupper end portion ofa 6 discharge pipe 28,which has its lowerend submerged in a bath 30 of molten zinc as in the construction previously described. Thus a vapor trap of molten zinc is formed and maintained in thewell 46 for the purpose already described.

The rising portion of the vacuum pipe 11 above the constant temperaturebath is cooled to form a trap for zinc vapor similarly to the pipe 11 in Figure l and any suitable means such as those already described are provided for periodically dislodging the zinc metal which thus collects on the wall of' the pipe. The metal sodislodged falls into the bottom of the U bend and is there melted whereby it passes into the well46.

In the further modified construction shown in Figure 6, the distributing tube 13 forms; the lower portion of the chamber and the annular well for the incoming metal surrounds only the upper portion of this tube.

This construction enables the outer surface of the distributing tube to be heated directly by burner gases, not only to compensate for the loss of heat from the bullion due to evaporation of'the zinc, but also to enable the outgoing bullion to be maintained at any desired temperature independently of the temperature of the incoming bullion. Thus when this construction is used, the incoming bullion may be supplied at a lower temperature than that required for satisfactory operation of the apparatus shown .in Figure 1.

Figure 6 also shows a further method of removing the recovered zinc by dissolving same in softened lead bullion which requires an addition of zinc for the succeeding desilverising operation.

For this purpose the vacuum pipe 111 extends centrallydownwards from the bottom of the chamber 10 and con-- stitutes an upward continuation of a vertical discharge pipe 50 for the softened bullion, the lower end of such pipebeing submerged in the bath 51. a

Softened bullion is supplied through a pipe 52 which extends vertically upwards within the pipe 50 and which is fitted at its upper end with a=distributing disc 53 over which the metal flows to fall from the periphery thereof in the form of a cylindrical-curtain.

The'vacuum line is continued by a pipe 11' which extends laterally through the wall of the lower end portion of the pipe 11 and below the distributing disc- 53 so that the vapors and gases withdrawn from the chamber 10 through the pipe 11 must pass through the curtain of softened bullion in order to enter the pipe 11".

The liquid zinc which falls from the condensing surface Within the chamber 10 falls directly into and isincorporated in the softened bullion in the manner which will be apparent from the drawing.

Figure 7 shows the provision on the inner surface of the distributing tube 11: of a helical channel 13 for the descending molten metal. In this case the molten metal instead of. overflowing the top of the distributing tube fromthe surrounding well, passes into the upper end of the helical channel 13 through an aperture 13 formed in: the wall of the tube. It will be evident that the exposed surface area of the" bullion in the channel is considerabl'e and also that the metal therein is maintained thereby in contact with the wall of the tube to absorb li'eat therefrom.

Figure 7 also shows still another method of removing the recovered zinc by causing the molten metal which drops from the condenser to fall through a barometric column 56 of a suitable oil maintained at a relatively low temperature into a tray 57 from which the inc which solidifies in passing. through the oil may be raked out at intervals.

Alternatively, and as indicated in Figure 8, the molten zinc which falls from the condenser descends through andsolidifies in a body 56 of oil which is maintained: at a suitably low temperature andis then-remelted ina heated downward extension of the pipe, so that the zinc is finally discharged in'the liquid condition as in the apparatus illustrated in Figure 1.

What is claimed is: 1. The method of separating and recovering a relatively volatile constituent from a molten metal complex con-' taining the same in association with a less volatile constituent, comprising causing the molten metal to pass sub stantiallycont'muously downwards in an attenuated condition in a substantially vertically extending evaporating zonewithin an enclosed space, maintaining within said enclosed space, and substantially in lateral opposition to saidevaporating zone, a substantially vertically extending solid mass of the same metal as said volatile constituent, maintaining said enclosed space under a low pressure such that the volatile constituent is progressive- 1y evaporated from said complex and condensed on said solid mass of metal, the surface of the latter being thus normally maintained by deposition of solid condensate and sequentially by remelting thereof in such relationship to the evaporating zone that the said surface is molten, whereby said volatile constituent is normally condensed in the liquid condition on the solid metal and flows downwardly thereover and separately progressively discharging said liquid condensate and said treated molten metal from the enclosed space.

2. The method-of separating and recovering zinc'from lead containing same comprising substantially continuously supplying molten zinciferous lead to an-enclosed space, causing the molten metal to descend in an attenuated condition within said space, substantially continuously discharging molten lead low in zinc from said enclosed space, maintaining said enclosed space under a low pressure such that zinc is progressively evaporated from the molten lead as it descends therein and maintaining in lateral opposition to said descending molten metal, a vertically elongated mass of solid zinc so that zinc vapor is progressively condensed thereon, whereby when the temperature of the surface of said zinc mass is less than the melting point of zinc, the zinc vapor is condensed thereon in'solid condition so that the surface of the zinc mass progressively extends into closer proximity to the descending molten lead until the condensing surface is at the temperature of the melting point of zinc and whereby when the temperature of said surface of the zinc mass tends to exceed the melting point of zinc, the said surface tends to recede from the descending molten lead due to the remelting of solid zinc, collecting the molten zinc which condenses on and which falls from the zinc mass and separately substantially continuously discharging such molten zinc from the evacuated enclosed space.

3. The method of separating and recovering zinc from molten lead containing same comprising causing the molten metal to flow downwardly in a substantially vertical and substantially cylindrical evaporating zone within an enclosed space, the temperature of such molten lead as it enters said evaporating zone being of the order of about 500 C. to 700 C., maintaining a vertically extending solid mass of zinc within and in lateral opposition to said evaporating zone, maintaining said enclosedspace at a vpressure below 500 microns of mercury such that zinc is progressively evaporated from the molten lead in said evaporating zone and is progressively condensed in the liquid conditionlon the surface of said solid mass of zinc and separately progressively discharging molten zinc and molten lead low in zinc from the enclosedspace, the temperature of the condensing surface being maintained approximately at the melting point of zinc by condensation of zinc in solid condition thereon when the temperature falls and by the remelting of solid zinc from such tinuously supplying molten zinciferous lead at a temperature of from 500 C, to 700 C. to an enclosed space,

causing the molten metal to pass downwardly within said space in the form of a thin tubular stream, substantially continuously discharging molten lead low in zinc from the bottom of said enclosed space, maintaining said enclosed space under a pressure, within the range 10-100 microns of mercury, such that zinc is progressively evaporated from the molten lead as it passes downwards therein, maintaining at a temperature below the melting point of zinc a vertically elongated condensing surface disposed Within the thin tubular stream in said enclosed space, initially depositing condensed zinc vapor in the form of a solid condensate layer thereon, continuing the deposition of solid zinc with consequent increase in the thickness of such layer to the formation of a cake of solid zinc, the thickness of which progressively increases until the exposed surface of the'cake has extended to a proximity to the descending tubular stream of molten lead such that said exposed surface is at the temperature of the melting point of zinc, thereafter depositing zinc in molten state on said exposed surface, collecting the molten zinc which subsequently deposits on and falls from the surface of the zinc cake, and separately substantially continuously discharging the collected molten zinc from the evacuated enclosed space. I

5. Apparatus for the separation and recovery of a relatively volatile constituent from a molten metal complex containing the samein association with a less volatile constituent, comprising a vacuum chamber, means forming a vacuum off-take passage an end of which communicates with the interior of said chamber, a substantially vertically disposed hollow condenser within said chamber, means for circulating a fluid coolant through said hollow condenser, said hollow condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid cake composed of said relatively volatile constituents to provide a condensing surface on which volatilized relatively volatile constituent may be condensed, a substantially vertical downwardly convergent frusto-conical distributing tube surrounding and spaced from the condenser and having its upper end disposed in a horizontal plane, the upper end portion at least of said tube being spaced from the wall of the container to form therebetween an annular reservoir for the molten metal, means for progressively supplying to said reservoir the molten metal to be treated whereby it overflows said upper end of the tube and then flows downwardly over the inner surface of the latter in the form of a thin tubular stream from which said volatile constituent progressively evaporates and progressively condenses on the opposed condensing surface in the liquid condition, means for progressively discharging the treated molten metal low in said volatile constituent from the lower end of the chamber and means for separately collecting and progressively discharging from the chamber, liquid relatively volatile constituents falling from such condensing surface.

6. Apparatus for the separation and recovery of a relatively volatile constituent from a molten metal complex containing the same in association with a less volatile constituent, comprising a vacuum chamber, means forming a vacuum off-take passage an end of which communicates with the interior of said chamber, a substantially vertically disposed hollow condenser pendant from the top of the chamber and terminating above the bottom thereof, means for circulating a fluid coolant through said condenser, said condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid-cake composed of said relatively volatile constituent to provide a condensing surface on which volatilized relatively volatile constituent may be condensed, a substantially vertical distributing tube surrounding and spaced from the condenser, means for progressively supplying molten metal to be treated to the inner surface of the upper end portion of the tube whereby it flows downwardly in contact with said inner surface thereof, means for discharging the treated molten metal from the lower end' portion of the vacuum" chamber, the volatile constituent being pr'ogressivcly evaporated from the molten metal as the latter descentls within the tube and progressively condensedon said condensing surface, the condensate being depositedin the solid form when the surface thereof is not disposedin such: close proximity to said tube that said condensing surface is molten, means for progressively collecting and discharging from the vacuum chamber the molten metal which condenses in the liquid condition on, and flows downwardly over, the condensing surface when the latter is molten and means for progressively discharging from the lower end of the chamber the treated molten metal low in said volatile constituent.

7. Apparatus for the separation and recovery of a relatively volatile constituent from amolten metal complex containing thesamein association with a less volatile constituent comprising avacuurn chamber, means forming a vacuum off-take passage an end of which communicates' with the interior of the chamber, a substantially vertically disposed hollow condenser' arranged approximately centrally within the chamber, means for circulating a fluid coolant through said condenser, said condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, al relativ'ely thick solid cake composed of said relatively 'volatile' constituent to provide a condensing surface on which volatilized relatively volatile constituent may be condensed, means forming around and spaced from the condenser a substantially cylindrical vertically extending evaporating zone, means for continuously supplying molten metal: to be trea ted to the upper end portion of said evaporating zone whereby it passes downwardly therethrough in lateral opposition to such condensing surface so that during the operation of the apparatus such condensing surface is maintained, by sequential condensation of solid metal and remelting thereof, approximately at the temperature of the melting point of the volatile constituent whereby the latter is condensed in the liquid condition and gravitates from such condensing surface, means forming a passage for discharging the molten metal low in said volatile constituent from the lower end portion of the chamber and means forming a passage for separately discharging said liquid condensate from the chamber.

8. Apparatus for the separation and recovery of zinc from molten lead containing the same comprising a vacuum chamber, means forming a vacuum oif-take passage an end of which comunicates with the interior of the chamber, a substantially vertically disposed condenser arranged approximately centrally within the chamber,

said condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid cake of zinc to provide a condensing surface on which volatilized zinc may be condensed, said condenser being hollow whereby a fluid coolant may be circulated therethrough, means forming within the chamber and around and spaced from the condenser a substantially cylindrical, vertically extending evaporating zone, means for continuously supplying the said molten lead to and distributing same around the upper end por tion of the evaporating zone whereby it descends therein in lateral opposition to the such condensing surface, means for discharging the molten lead low in zinc from the lower end portion of the chamber and means for separately discharging molten zinc from the lower end portion of the chamber.

9. Apparatus for the separation and recovery of a relatively volatile constituent from a molten metal complex containing the same in association with a less volatile constituent comprising a vacuum chamber, means forming a vacuum off-take passage an end of which communicates with the interior of the chamber, a substantially through, said condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid cake composed of said relatively volatile constituent toprovide a condensing surface on which volatilized relatively volatile constituent may be condensed) means forming a substantially cylindrical and substantially vertically disposed distributing surface around and spaced from such condensing surface, means for continuously supplying molten metal to be treated to and distributing same around the upper end portion of said distributing surface whereby it gravitates thereover in lateral opposition to"s'uch= condensing surface, means forming below the condenser a descending passage for discharging liquid condensate from the chamber, a laterally extending heat c'onductivemember above and spaced from the top of said passage, said heat conductive member being also disposed below and spaced from the condenser whereby liquid condensate falling from such condensing surface is received on said heat conductive member and flows laterally thereover to enter said discharge passage and whereby metal vapor ascending in said passage is condensedon the lower surface of said heat conductive member, and means forming a passage for separately discharging molten metal low in said volatile constituent from the lower end portion of the chamber. o

10, Apparatus for the separation; and recovery of a relatively volatile constituent from a molten metal complex containing thesame in association with a' less volatile constituent, comprising a vacuum chamber, a substantially vertically disposed condenser depending from the top of the chamber, said condenser being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid cake composed of said relatively volatile constituent to provide a condensing surface on which volatilized relatively volatile constituent may be condensed, said condenser having its lower end disposed above the bottom of the chamber and being formed centrally with a vacuum off-take passage which extends upwards from the lower end thereof, said condenser being hollow whereby a fluid coolant may be circulated therethrough and around said central passage therein, means providing around and spaced from such condensing surface, a substantially cylindrical vertically extending and inwardly facing distributing surface, means for supplying the molten metal complex to the upper end portion of said distributing surface whereby it flows downwardly in contact with said surface, means for discharging from the chamber the liquid condensate which falls from such condensing surface, and means for separately discharging, from the lower end portion of the chamber the treated molten metal low in said volatile constituent.

11. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex containing the same in association with a less volatile constituent comprising a vacuum chamber, a substantially vertically disposed condenser depending from the top of the chamber and having its lower end disposed above the bottom of the chamber, said condenser being adapted to support on its outer peripheral surface, during oper ation of the apparatus, a relatively thick solid cake composed of said relatively volatile constituent to provide a condensing surface on which volatilized relatively volatile constituent may be condensed, said condenser having therein a central vertical vacuum off-take passage which communicates at its lower end with the interior of the chamber, said condenser being hollow whereby a fluid coolant may be circulated therethrough and around said central passage, a downwardly convergent frusto-conical distributing tube arranged vertically about and spaced from the condenser and having its upper end arranged horizontally below the top of the chamber, said distributing tube being connected at its lower end to the bottom of the chamber and being spaced inwardly from the wall of the latter whereby an annular well is formed therebetween, means for continuously supplying lower end of the chamber and means forming a passage for separately discharging from the chamber liquid relatively volatile, constituent falling from such condens ing surface..

12. Apparatus according to claim 11 including a vertically movable scraper arranged within said vacuum off-take passage to remove solid condensate from the wall thereof.

13. Apparatus according to claim 11 wherein said passage for the discharge of liquid relatively volatile constituent communicates with the bottom of the chamber directly below the ,condenser and including a later- .vergent frusto-conical condenser core depending from the top of the chamber and having its lower end disposed above thebottom ofthechamber, said condenser core being hollow and provided with means whereby a fiuid coolant may be circulated therethrough, said condenser core being adapted to support on its outer peripheral surface, during operation of the apparatus, a relatively thick solid cake composed of zinc to provide a. condensing surface on, which volatilized zinc may be condensed,

means forming a central vertical vacuum oft-take passage through said condenser core which passage communicates at its lower end with the interior of said chamber, a downwardly convergent frusto-conical distributing tube arranged about and spaced from said condenser core and having its upper end arranged horizontally, said distributing tube being connected at its lower end to the bottom of the chamber and being spaced inwardly from the wall of the latter whereby an annular well is formed therebetween, means for continuously supplying molten lead to said well whereby when the latter is full it continuously overflows the upper end of said distributing tube and flows downwardly over the inner surface of the latter in the form of a thin sub stantially tubular stream from which latter the zinc volatilizes and then condenses on the opposed condensing surface, means forming a passage for discharging molten lead low in zinc from the lower end of said chamber and means forming a passage for separately discharging from the chamber liquid zinc falling from such condensing surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,126,467 Hickman Aug. 9, 1938 2,239,370 Osborn et al Apr. 22, 1941 2,615,706 Davey Oct. 28, 1952 

1. THE METHOD OF SEPARATING AND RECOVERING A RELATIVELY VOLATILE CONSTITUENT FROM A MOLTEN METAL COMPLEX CONTAINING THE SAME IN ASSOCIATION WITH A LESS VOLATILE CONSTITUENT, COMPRISING CAUSING THE MOLTEN METAL TO PASS SUBSTANTIALLY CONTINUOUSLY DOWNWARDS IN AN ATTENUATED CONDITION IN A SUBSTANTIALLY VERTICALLY EXTENDING EVAPORATING ZONE WITHIN AN ENCLOSED SPACE, MAINTAINING WITHIN SAID ENCLOSED SPACE, AND SUBSTANTIALLY IN LATERAL OPPOSITION TO SAID EVAPOPRATING ZONE, A SUBSTANTIALLY VERTICALLY EXTENDINGB SOLID MASS OF THE SAME METAL AS SAID VOLATILE CON STITUENT, MAINTAINING SAID ENCLOSED SPACE UNDER A LOW PRESSURE SUCH THAT THE VOLATILE CONSTITUENT IS PROGRESSIVELY EVAPORATED FROM SAID COMPLEX AND CONDENSED ON SAID SOLID MASS OF METAL, THE SURFACE OF THE LATTER BEING THUS NORMALLY MAINTAINED BY DEPOSITION OF SOLID CONDENSATE AND SEQUENTLY BY REMELTING THEREOF IN SUCH RELATIONSHIP TO THE EVAPORATING ZONE THAT THE SAID SURFACE IS MOLTEN. 